1. Field of the Invention
The present invention relates to a method, an apparatus, and the like for transmitting a plurality of pieces of image data after adding an electronic signature thereto.
2. Description of the Related Art
Image forming apparatuses having a variety of functions, such as copying, network printing, scanning, faxing, and Transmission Control Protocol/Internet Protocol (TCP/IP) communication have recently come into widespread use. Such image forming apparatuses are sometimes called “Multi-Function Peripherals (MFPs)”, “multifunction devices”, or the like.
The functions of such image forming apparatuses, and peripheral technologies have recently been advanced. Thanks to the advancements, for example, image data that has been obtained by using a scanning function can be converted into image data in various formats, e.g., Tagged Image File Format (TIFF) or Portable Document Format (PDF). Such image forming apparatuses employ, as a TCP/IP application, an application for sending and receiving electronic mail and an application for sending and receiving data through FTP.
This enables a user to transmit image data that has been obtained by using the scanning function to other devices in various combinations of formats and transmission methods.
There is proposed an image forming apparatus capable of adding an electronic signature to image data in order to improve the reliability of communication (Japanese Laid-open Patent Publication No. 2003-224728).
According to the image forming apparatus described in Japanese Laid-open Patent Publication No. 2003-224728, a USB token is inserted into a USB connector of the image forming apparatus, and a document is scanned. Then, a scan data processing unit of a data processing apparatus converts an image obtained by scanning the document into a document file, and a message digest generation unit of the data processing apparatus calculates a message digest. Then, an encryption unit of the image forming apparatus uses a private key obtained from the USB token to encrypt the message digest received from the data processing apparatus. After that, a signed message digest is combined with the document file in the data processing apparatus, so that a signed document file is generated.
As discussed above, in recent years, it has come to be possible to transmit one piece of image data to other devices in various combinations of formats and transmission methods. This increases the time for a USB token to be used. In the case where a private key of a user who is logging on an image forming apparatus is read out from a certificate store of the image forming apparatus instead of from a USB token, and the private key thus read out is used, the time necessary for the user to log on the image forming apparatus is longer than before.
Meanwhile, a private key should not be leaked out. In view of this, the time for a USB token to be set to a USB connector is preferably short in order to prevent a user from failing to bring back the USB token, someone from carrying away the USB token inadvertently, or someone from stealing the USB token.
Further, it is desirable for a user to log out of an image forming apparatus promptly after transmission of image data in order to prevent someone from using or copying a private key of the user.